Conventional grafting-to approaches to DNA-polymer conjugates are often limited by low reaction yields due to the sterically hindered coupling of a pre-synthesized polymer to DNA. The grafting-from strategy, in contrast, allows to directly graft polymers from an initiator that is covalently attached to DNA. Herein, we report blue light-mediated reversible additionfragmentation chain-transfer (Photo-RAFT) polymerization from two different RAFT agentterminated DNA sequences using Eosin Y as the photocatalyst in combination with ascorbic acid. Three monomer families (methacrylates, acrylates and acrylamides) were successfully Max Planck Institute for Polymer Research-Author's Manuscript 2 polymerized from DNA employing Photo-RAFT polymerization. We demonstrate that the length of the grown polymer chain can be varied by altering the monomer to DNA-initiator ratio, while the self-assembly features of the DNA strands were maintained. In summary, we describe a convenient, light-mediated approach towards DNA-polymer conjugates via the grafting-from approach. Introduction The combination of synthetic polymers with the unique specificity and recognition properties of DNA gave rise to an all-new class of DNA-polymer hybrid materials. 1-5 In recent years, DNApolymer conjugates have emerged as versatile building blocks that provided enhanced stability to complex DNA nanostructures 6,7 or facilitated, e.g., the precise organization of polymeric structures by DNA. 8-12 In particular, the combination of DNA with a hydrophobic polymer chain resulted in amphiphilic species that formed supramolecular architectures such as micelles or vehicles. 13-15 These assemblies were intensively investigated in the context of drug delivery, 16-19 as scaffolds for directing organic reactions 20 or as virus-like particles. 21 Inspired by recent advances in designing more sophisticated 2D and 3D DNA architectures equipped with various functionalities, 22,23 polymer chains were organized within complex DNA scaffolds or grown from DNA origami templates in distinct nanostructures. 24,25 Until recently, grafting-to strategies of pre-synthesized polymers to DNA sequences were mainly accomplished following solid phase synthesis 13,20,26,27 or bioconjugation strategies, such as copper-mediated azide-alkyne, 28,29 thiol-ene, 30-32 amide 33-35 or recently also tetrazine-norbornene coupling. 36 While the major advantage related to both approaches is that the polymer can be thoroughly characterized prior to the coupling reaction, the nature of the polymer has to be Max Planck Institute for Polymer Research-Author's Manuscript 3 carefully selected, e. g., it must remain stable under the strongly basic conditions of DNA-cleavage from the solid support. Critically, variation of polymer lengths to, i.e., improve stability and bioactivity is more tedious via the grafting-to strategy and low reaction yields were reported. 32,37 Most likely, steric hindrance of the pre-formed polymer chain or the necessity to use organic solvents during the conjugation step caused ...

The actin cytoskeleton is of fundamental importance for cellular structure and plasticity. However, abundance and function of filamentous actin in the nucleus are still controversial. Here we show that the actin-based molecular motor myosin VI contributes to the stabilization of stalled or reversed replication forks. In response to DNA replication stress, myosin VI associates with stalled replication intermediates and cooperates with the AAA ATPase Werner helicase interacting protein 1 (WRNIP1) in protecting these structures from DNA2-mediated nucleolytic attack. Using functionalized affinity probes to manipulate myosin VI levels in a compartment-specific manner, we provide evidence for the direct involvement of myosin VI in the nucleus and against a contribution of the abundant cytoplasmic pool during the replication stress response.